CHANGES IN LIGHT BELOW THE CANOPY OF A JAMAICAN MONTANE RAIN-FOREST AFTER A HURRICANE

Hurricane Gilbert caused disturbance to Jamaican montane rainforests i n 1988. This study provides a detailed characterization of landscape-l evel changes in light below the canopy of these forests after the hurr icane. Hemispherical photographs were taken below the forest canopy at four sites at permanent points 1 m above the ground between 7 and 33 mo after the hurricane. For each photograph photosynthetically active radiation (PAR) was computed. PAR declined exponentially in all sites during the period of measurement. During the first 24 mo after the hur ricane, PAR beneath the canopy was significantly greater in sites that had been defoliated during the hurricane than in sites where few tree s bad been defoliated. By 28 mo after the hurricane there was no signi ficant difference in PAR beneath the canopy among the four sites. By 3 3 mo after the hurricane canopy recovery was nearly complete and PAR w as only slightly higher than measurements made before the hurricane. O ur results were compared with studies of changes in light environment resulting from treefall gaps and under deciduous canopies. PAR during the first 18 mo after the hurricane was similar to that recorded in sm all canopy gaps in other forests. widespread defoliation caused by hur ricanes can thus increase PAR beneath the canopy over large areas and consequently opportunities may arise for widespread recruitment of tre e species in response to increased light levels.